Line cutter



United States Patent 3,369,296 LINE CUTTER Albert T. Takahashi,Torrance, and Ronald E. Gardner,

Lomita, Califi, assignors to Hi-Shear Corporation, Torrance, Califi, acorporation of California Filed Jan. '12, 1966, Ser. No. 520,138 6Claims. (Cl. 30-228) ABSTRACT OF THE DISCLOSURE This invention relatesto a line cutter in which a body has a bore with an axis along which acutter plug can be fixed to cut a line which passes transversely throughthe bore. A choke is disposed in the path of the cutter plug todecelerate the same by extrusion, or change of cross-section. However,the choke is not contacted by the cutter plug until the trailing edge ofthe cutter plug passes an edge of -a port through which the line entersthe bore, whereby the propellant gases are vented before the cutter plugis clecelerated.

This invention relates to a cutter for severing lines such as nylonreefing lines, and electrical wiring.

There are numerous situations in which it is desirable to cut a lineupon receiving a signal for that purpose. One example is found incutting reefing lines of parachutes so as to release a cargo. Another isto sever an electrical wire at a preselected time so as to break acircuit. It is an object of thisinvention to provide a reliable deviceof this type.

An optional object of this invention is to provide a device of this typewhich can utilize an explosive charge, and which is essentiallyself-contained both before and after actuation.

A cutter according to this invention comprises a body having an internalbore with an axis and with a line passage extending transversely throughthe body and the bore to receive a line to be cut. A cutter plug makes afluid-sealing, slidable fit in the bore to one side of the line passage.A charge is provided for releasing gas into the bore on the oppositeside of the plug from the line passage, whereby gas pressure from thecharge propels the plug to sever a line that is passed through the linepassage by shearing the line between the plug and the body at the linepassage.

According to a preferred but optional feature of this invention, a chokeis formed internally in the bore on the opposite side of the linepassage from the plug whereby the plug is extruded by the choke afterthe line is severed, thereby to decelerate and retain the plug in thebody.

According to still another preferred but optional feature of theinvention, the charge is an explosive material.

The above and other features of this invention will be fully understoodfrom the following detailed description and the accompanying drawings inwhich:

FIG. 1 is an axial cross-section of the presently preferred embodimentof the invention;

FIG. 2 is a perspective view of a portion of FIG. 1;

FIG. 3 is a righthand end view of FIG. 1;

FIG. 4 is a fragmentary cross-section of the device of FIG. 1 afteractuation; and

FIG. 5 is a side elevation of the device of FIG. 1 after actuation.

As can best be seen in FIG. 1, a cutter according to the inventionincludes a body 11 having an internal bore 12. The bore has a centralaxis 13 and is preferably cylindrical. A line passage 14 includes firstand second ports 15, 16, so that a line 17 can be passed through theline passage and through the bore. Preferably the line passageintersects the central axis at right angles.

A cutter plug 18, preferably of extrudable material such as nylon orother plastic material, is placed in the bore adjacent to an intern-a1chamfer 19'. The cutter plug includes a chamfer 20 to abut chamfer 19.The plug makes an interference fit so that it makes a fluid-sealing,slidable fit with the wall of the bore. It is axially slidable therein.

A choke 25 is formed at open end 26 of the bore. A choke is bydefinition a reg-ion of lesser lateral dimension than the bore. It maybe formed by staking in a lip 27 (or lips) or it might be formed by amachined shoulder. The choke need not be completely peripheral butpreferably it is. The object of the choke is to cause the plug to beextruded through a region of a lesser lateral dimension than its own,thereby to dissipate the kinetic energy of the plug and to prevent itsexpulsion from the body. This type of deformation dissipates the energyin such a way as to prevent the plug from making a sharp blow on thebody. Energy dissipated in deformation is not transmitted to the body asa shock load. This is advantageous, because there will then be a lesserreaction on the body and on surrounding structure.

Energy for severing the line is provided by means of a source of gasunder pressure. The preferred source is a squib 30 which comprises acharge of explosive material. The squib is placed in the bore adjacentto chamfer 19 and is packed against a ceramic header 31 which closes theleft-hand end of the bore. The header is potted in place by an epoxybarrier 31a. The header supports a bridgewire 32 which is in contactwith the explosive material 33. Two electrodes 34, 35 are provided sothat the squib can be connected to a source of electrical energy forfiring the same. They extend through the header and the barrier. Athreaded neck 36 protects the electrodes and provides means forattachment of the electrodes. A pair of external grooves 37, 38 isprovided to aid in attaching the reefer cutter to other structure suchas by tying it to said other structure with wire, clamps, or otherfastening means.

The device is shown in FIG. 1 in its repose condition, the line to becut having been threaded through the transverse line passage. The cutterplug makes a complete environmental seal for the squib so that .nofurther care need be taken as to the squib itself. So long as the deviceremains in this condition, the line remains continuous and the linecutter simply remains in place.

When a firing current is passed through the bridgewire, the explosivematerial generates a quantity of gas under pressure and fires the plugto the right in FIG. 1. The plug shears off the line at the two pointsof intersection of the ports and the wall of the bore. The portion ofthe line which is cut out is simply pushed ahead of the plug, butbecause it is light, it does no harm if it leaves the body. The plugcontinues to move to the right. After it passes the line passage, thegas pressure behind it is released. The kinetic energy of the plug isdissipated by extrusion at the choke, the result of which is shown inFIGS. 4 and 5 where a neck 39 has been formed on the plug. Thus thefast-moving plug cannot leave the device to strike and perhaps damageadjacent structure.

Line 40 as shown in FIG. 5 is severed into two pieces 41, 42, which willeasily fall away from the cutter because there is nothing to hold it inplace. It is evident that it is only necessary to provide suflicientstrength in the plug and sufiicient energy in the gas-generating chargeto exercise a shearing action on the line. The force required isdetermined by the material which is to be cut. This can readily bedetermined by a few trials. Overdesign of the explosive charge will dono harm because of the retention effect of the choke. Any gas-generatingsource is suificient, but a good example of a suitable squib will befound in United States Patent No. 3,135,200 issued to Jackson on June 2,1964. In addition to explosive charges, gas-release cartridges and thelike may also be used.

This device has many advantages, one being that a circular plasticcutter may be used instead of the usual steel chisel blade and anvilutilized in line cutters. In blades and anvils the resulting percussiveeffect is often undesirable and, furthermore, the compression of thematerial between the chisel .blade and the anvil sometimes interfereswith the actual severance thereof. A good environmental seal is providedby the plug, thereby rendering the squib quite reliable. The temperaturerange of the device is great. The device has been operated over therange from 65 to +200 F.

This invention is not to be limited by the embodiment shown in thedrawings and described in the description which is given by way ofexample and not of limitation, but only in accordance with the scope ofthe appended claims.

We claim:

1. A cutter for severing a flexible line, comprising: a body having abore with an axis and a line passage passing transversely through thebody and the bore, thereby forming two aligned ports in the body, thepassage having a first and a second end, the ports lying between theends; a cutter plug of extrudable material making a fluidsealingslidable fit in said bore and adapted initially to be placed between thefirst end and the ports; a source for supplying gas under pressure tothe bore at the first end in order to propel the cutter plug against aline passing through the ports and bore by shearing the same at thejunctions of the ports and the wall of the bore; and a choke comprisinga reduction in at least one lateral dimension of the bore such as tochange the cross-section of at least a portion of the cutter plug asthis portion passes through the choke, the cutter plug having a dimen-4; sion of length of its portion making said fluid seal, and the chokebeing axially spaced from the edge of the ports nearest the first end bya distance which is no less than said dimension of length, whereby theend of the fluidsealing portion of the cutter plug nearest the first endpasses the said edge of the ports and releases the gas pressure on thecutter plug no later than the time the cutter plug engages the choke,whereby gas pressure on the cutter plug is relieved while the chokedecelerates the cutter plug, the bore being clear to the lateraldimensions of the choke for a suificient distance to leave axiallyunobstructed the portion of the cutter plug which is extruded.

2. A cutter according to claim 1 in which the plug makes an interferencefit with the bore.

3. A cutter according to claim 1 in which the source is an explosivematerial.

4. A cutter according to claim 1 in which the choke comprises aninwardly extending portion of the body.

5. A cutter according to claim 1 in which the bore is open at its end onthe other side of the line passage from the plug.

6. A cutter according to claim 1 in which the plug is made of anextrudable plastic material.

References Cited UNITED STATES PATENTS 2,140,214 12/1938 Temple.

2,920,532 1/1960 McBride.

2,924,147 2/1960 Bohl et al.

OTHELL M. SIMPSON, Primary Examiner.

WILLIAM FELDMAN, Examiner.

I. C. PETERS, Assistant Examiner.

